Cutting-Edge Sensors and Software Tests
Will Help Protect Pentagon from Airborne Hazards

April 23, 2004

BOULDER—A breakthrough blend of high-tech instruments and
weather forecasting models is being tested at the Pentagon April
15–May 15. Coordinated by scientists at the National Center
for Atmospheric Research (NCAR), the tests scan for potential airborne
toxins near the Pentagon and predict their motion and impact on
the building. The knowledge gained from the tests will allow the
development of improved systems for protecting Department of Defense
facilities.

Partners from academia and the public and private sector are joining
NCAR in the effort, sponsored by the Defense Advanced Research
Projects Agency (DARPA). NCAR brings to the test years of experience
in developing systems that detect and warn for wind shear and turbulence
at airports and protect against terrorism at high-profile events,
such as the Olympic Games.

The Pentagon

"Knowing how to properly respond to an attack or a toxic
industrial incident requires the best modeling tools and sensors
available today, and these must all work in a coordinated fashion
in real time," says NCAR project leader Scott Swerdlin.

Understanding air circulation around the Pentagon is a unique
challenge, says Swerdlin. The air circulations are very complex
because of the building's size and unusual geometry. Temperature
inversions, especially at night, could allow an airborne hazard
to spread below rooftop height, which adds to the complexity of
a monitoring system.

To tackle the problem, NCAR and partners built a nest of concentric
computer models—each with a different strength—that
predict weather conditions from the entire Washington region inward
to the Pentagon itself. Information is routed among them every
15 minutes.

"The weather modeling system tested here is one of the most
complex ever constructed," says NCAR's Thomas Warner, lead
scientist on the project.

DARPA program manager Paul Benda adds, “The weather modeling
system being tested will greatly improve our understanding of how
to best protect the occupants of the Pentagon from a chemical or
biological attack.”

This spring's
testing

Tests will occur between April 15 and May 15. In addition to the
system's standard equipment (below), these tests will include

A 23-foot-long instrumented balloon tethered above the Pentagon.
Deployed by the University of Colorado, the setup includes sensors
studded along the balloon's tethering wire. As the balloon rises
and falls, the sensors sample air flow and turbulence.

Periodic releases of sulfur hexafluoride (SF6). This inert,
invisible, nontoxic gas helps scientists verify the accuracy
of the computer models and sensors that track dispersal of airborne
material. The releases are coordinated by the National Oceanic
and Atmospheric Administration with assistance from the U.S.
Army's Dugway Proving Ground.

The dates of the SF6 releases hinge on day-to-day weather conditions.
Scientists are taking advantage of wind directions and speeds that
allow SF6 to be tracked from a release point directly toward the
Pentagon.

"It's a very challenging exercise," says Swerdlin. "We’re
calling on a lot of experienced players and advanced weather forecasting
systems in order to precisely time the releases."

What's in the
system

Most modern weather forecasts target areas the size of a county,
not a single building. NCAR and colleagues are developing a unique,
fine-scale weather monitoring and forecasting system. It includes

A multiscale weather forecast model. Every 15 minutes, this
software pulls information from a high-resolution regional weather
analysis and generates a set of wind forecasts with increasingly
finer detail at smaller scales. The forecasts draw on data from
Doppler radars as well as lidars (see below). At its finest scale,
the system charts air flow every 7 feet (2 meters) immediately
around the Pentagon.

Lidars (laser-based radars). With a beam narrower than that
of conventional radar, a lidar is ideal for tracking tiny particles
at short distances in clear air. Coherent Technologies, Inc.,
is providing a Doppler lidar for monitoring winds, while NCAR
tests its new lidar suitable for tracking toxic clouds at very
fine scales.

Other sensors. Local weather stations and sensors are designed
to spot airborne toxins as they pass a single point.

The National Center for Atmospheric Research and
UCAR Office of Programs are operated by UCAR under the sponsorship
of the National Science Foundation and other agencies. Opinions,
findings, conclusions, or recommendations expressed in this publication
do not necessarily reflect the views of any of UCAR's sponsors.